Bench marks in sheet or web material



United States Patent [72] Inventors Rene Larive GrandMere, Quebec,Canada, and Leo-Paul Gelinas, North Syracuse, N.Y., Richard L. C.Knight, GrandMere,

- Quebec, Canada [21] Appl. No. 719,954

[22] Filed Apr. 9,1968

[45 Patented Dec. 22, 1970 [73] Assignee Consolidated Paper (Bahamas)Limited Nassau, Bahamas [54] BENCH MARKS IN SHEET OR WEB MATERIAL 8Claims, 5 Drawing Figs.

[52] US. Cl. 219/384, 2l9/l21:264/154 [51] lnt.Cl H05b3/18 501 Fieldol'Search 219/384- [56] References Cited UNITED STATES PATENTS 2,205,2556/1940 Gulliksen 219/384 2,528,157 10/1950 Menke 219/384 2,550,3664/1951 Meaker et a1 219/384 2,683,208 6/1954 Andrews 219/384 3,167,6411/1965 Parmele et al.. 219/384 3,226,527 12/1965 Harding 219/3842,141,869 12/1938 Koenig 219/384 2,388,069 10/1945 Meaker et a1 219/3842,516,609 7/1950 Woodard..... 2l9/384X 2,982,186 5/1961 McKeen 219/384XFOREIGN PATENTS 430,177 8/1967 Switzerland 219/384 1,163,216 2/1964Germany 219/384 Primary Examiner-Volodymyr Y. Mayewsky Attorney-AlanSwabey ABSTRACT: A sheet or web of material with reference marks in theform of tiny perforations. The perforations are preferably formed bysparking holes through the web.

PATENTEnnEc22|9m 3.649.858

FIG. 5

L T RENL'xaW I Lab-PAUL GELINAS RICHARD L. c. KNIGHT BENCH MARKS INSHEET OR WEB MATERIAL This invention relates to providing a sheet or webof material with reference marks.

In the manufacture and use of sheet or web material such as paper orplastic film, it is desirable to provide reference marks on the materialin order to perform various operations. These operations can includeusing the reference marks to measure the length of the sheet or web, tomeasure their speed of travel during use, to provide accurateregistration of successive sheets or impressions on a continuous webduring their travel and even to identify the sheet or web.

Reference marks have been used in the past. However, all of thesepreviously used marks have disadvantages. Printed marks, because of themechanical nature of application, are difficult to apply when the sheetor web is travelling at high speed and are not too well defined.Further, printed marks can become disfigured and result in inaccuratemeasurements between one mark and the next. Watermarks, applied topaper, are too vaguely defined and are too large to provide accuratemeasurements. Any radioactive tracer material or magnetic material usedas a mark is usually applied in a mechanical fashion to the sheet orweb, and again this is not satisfactory for high speed operation. Manyreference marks, when applied, are visible and cannot be used when thesheet or web must have surfaces unmarked in appearance. One of the mostimportant disadvantages, particularly since most known reference marksare applied with mechanical means, is the time required for applying thereference mark on a web travelling at high speed from the instant acommand is given to apply the reference mark. Even if it only takes1/1000 second to apply the mark, for a web travelling at 2500 ft./min.,the web will have moved it inch in the time taken to apply the mark.

It is therefore an object of the present invention to provide referenceor reference marks in a sheet or web of material which overcome thedisadvantages of the prior art while providing positive advantages whichinclude ease of application, particularly when the sheet or web istravelling at high speed, which are not visible under casual observationand which do not substantially affect the quality of the sheet or web.

It is a more particular object of the invention to provide a sheet orweb of material having reference marks in the form of perforations. Theperforations can be provided at spaced locations on the sheet or web andpreferably are substantially circular having a diameter in the range offrom 0.002 inches to 0.02 inches.

It is another object of the invention to provide a method of referencemarking a moving sheet or web of material, particularly a sheet or webof material travelling at high speed, comprising forming perforations inthe material at spaced locations, the perforations being substantiallycircular and having a diameter in the range of from 0.002 inches to 0.02inches. Preferably, the perforations are formed by burning a holdthrough the sheet or web.

The perforations formed in the sheet or web material must be smallenough so that they are not normally visible to the naked eye so as todetract from the surface appearance of the sheet or web and yet arelarge enough to allow detection of the perforations through the use ofsensing means such as a light source and light detector. The size of theperforations will depend to some extent on the quality, nature andthickness of the web being perforated. Newsprint, for example, has morespecks of dirt in it than white bond quality paper and, for the samethickness of paper, larger perforations may be used in newsprint than inthe bond paper, since the perforations will not be as visible among thespecks in newsprint as on the clean surface of the bond. The larger theperforations, the easier they are to detect using the sensing means.

The invention is particularly useful in the papermaking industry. Theinvention allows many paper products, particularly those which must havean unmarked appearance, to be provided with reference marks. In themanufacture of a paper web, the marks can be used, for example, tomeasure the speed of travel of the web, the length of a web, and theamount of dimensional change in the web during its manufacture. Theperforations can be formed when the web is travelling at speeds up to20,000 ft./min. and when the web has a moisture content up to 60 percentby weight of water.

The invention will now be described in detail having reference to theaccompanying drawings, in which:

FIG. I is a plan view of a sheet or web material showing the referencemarks of the invention;

FIG. 2 is a cross-sectional view of the sheet shown in FIG. I takenalong line 2-2;

FIG. 3 shows an apparatus for applying the reference marks to a movingsheet or web of material;

FIG. 6 shows an apparatus for detecting the reference marks in a movingsheet or web of material; and

FIG. 5 shows an apparatus for applying a series of reference marks to amoving sheet or web of material.

FIG. 1 illustrates a sheet or web of material I which has referencemarks 3. The size of the reference marks are exaggerated in thedrawings. The sheet or web is a cellulose material, preferably paper,although other sheet or web materials such as thin plastic film can beprovided with the perforations also. As shown in FIG. 2, the referencemarks 3 consist of substantially cylindrical holes passing transverselythrough the web I. The holes preferably have a diameter at least equalto the thickness of the web or sheet material. The diameter of the holescan preferably range between 0.002 inches to 0.02 inches. If the holesare any smaller than 0.002 inches, they are extremely difficult todetect and therefore not useful as reference marks. If the holes arelarger than 0.02 inches, they can normally be seen by the naked eye andthus mar the appearance of the web. As shown in FIG. 1, the referencemarks may be applied in a line 5 extending parallel to the direction ofmovement of the web, as shown by the arrow in FIG. I, and can be equallyspaced from one another.

FIG. 3 illustrates one method of forming the perforations in thetravelling web. In this method, particularly suitable when the web is ofpaper, the perforations are made by burning through the web with aspark. Two electrodes 7, 9 are apart to form a gap 11 through which theweb travels as shown. Preferably, the gap between the electrode tips l3,15 is about 0.125 inches. The tips of the electrodes have a radius ofabout 0.0015 inches. One electrode is connected to ground. The other isconnected to a well-known capacitance discharge device 17 similar to thesystem used in an automobile ignition system. A battery or DC powersupply of approximately 400 volts is used to charge the capacitor. Whenthe capacitor is discharged, a spark will jump between the tips of theelectrode burning a hole in a paper web located between the electrodes.The time required to form the perforation from the instant a commandsignal is given would be approximately 20 microseconds. Because of therandom path travelled by the spark in passing between the electrodes,the perforation formed in the web is not always centrally located withrespect to the longitudinal center line of the electrodes. To minimizethe variations in the path of the spark, the web can be located closelyadjacent to the tip of one of the electrodes. The size of theperforation formed by spark burning can be controlled by the input powerand configuration of the spark producing circuit. The radius of theelectrode tips should preferably be kept as small as possible in orderto limit spark wander and more accurately control the placement of theperforation. Where very accurate placement of the hole is not asimportant, the size of the electrode tips may be made larger to increasethe life of the electrodes. Other known spark-producing means can beused which do not require a capacitor or DC power supply.

The perforations are easily detected by passing the web over a lightsource. As shown in FIG. 4, the light source 18 includes means foremitting light such as a light bulb 19 located adjacent one side of theweb. A cover 21 having a slit 23 is located between the light bulb andweb. On the other side of the web is a light detector 25 having a lens27 and a photomultiplier tube 29. When a perforation passes the slit 23,an image of the illuminated perforation is magnified by the lens 27 andis detected by the photomultiplier tube 29. Preferably, the slit 23 isapproximately 0.006 inches in width, and the photomultiplier tube 29 issensitive enough to detect the perforation passing across the slit inthe first 0.001 inch of its travel. The signal from the photomultipliertube can be amplifier and, depending on the use of the perforations, canbe transmitted to a counter for counting the perforations when measuringthe length of a web, can be used for measuring time intervals formeasurement of web velocity, or can be used in other ways which will beapparent.

The perforations formed by the spark may not always be perpendicular tothe web or sheet since the spark follows the line of least resistancethrough the material. Consequently, the perforation could be formed atan'angle to the plane of the web or sheet. Detection of the angledperforation by a light source is more difficult since the detectingmeans is arranged to operate along a line perpendicular to the plane ofthe sheet. If the diameter of the perforation is less than the thicknessof the web or sheet in which it is formed, and if it is formed at anangle, there is the possibility that the perforation may not bedetected. It is therefore preferred to form the perforations to at leasta diameter equal to the thickness of the web or sheet. The diameter maybe larger than the web or sheet thickness provided that it is not largeenough to detract from the appearance of the web or sheet.

The pattern and/or method in which the perforations are formed in theweb can vary depending on what they are used for. If it is desired, forexample, to measure the length of a web, the perforations are made atequally spaced intervals along the length of the web as shown in FIG. 1.To make the holes, an arrangement as shown in FIG. 5 could be used. Theelectrodes 7, 9 are located a spaced distance L from the center of theslit 23 in the light source 18. After a first perforation is formed bymanual operation of the sparking device 17, the following perforationscan be formed automatically. Passage of the first perforation past thedetector will trigger the sparking device 17 through line 30 to form.another perforation. The process of using the detection of eachpreviously formed perforation to form the next following perforationcontinues. Each detection of a perforation is counted by a counter 31.The distance L" between the detector and electrode tip is known. Thedistance L multiplied by the number of counts on the counter gives thelength of the web.

Other means besides burning the hole with a spark can be used to formthe perforations. For example, the perforations may be formed with alaser beam. The laser has the advantage over sparking in providing amore accurate placement of the perforation since it burns a holeperpendicularly through the web while the spark, following a line ofleast resistance, may form a perforation which is off center. However,the perforation produced by the laser has more ragged edges than asparked perforation and is not as well defined.

The perforations may be formed in pairs, the perforations in each pair aspaced known distance apart, extending either longitudinally ortransversely along the web. The pair of perforations may be appliedprior to, during, or after the drying of a web of paper. The distancebetween each pair can be measured during or after the drying operationand the difierence in the distance between the pair of holes when formedand when measured provides an indication of the dimensional change ofthe web. Thus, variations in the dimensional change can be used tocontrol the drying operation of a web to ensure even drying transverselyof the web. If the perforations are formed after drying, they may beused to measure dimensional changes in a roll of web material due tohumidity changes or mechanical set of web when in roll form prior to orduring use of the rolled web. The perforations can also be used tomeasure dimensional changes in a preprinted web or sheet between theprinting step and a subsequent printing step in order to properlyregister the web or sheets for the subsequent printing step.

When using a single longitudinal row of perforations and a singledetector, a perforation may miss being detected for some reason or thedetector may give a false reading on detecting a pin or blow hold formedin the material. To avoid such errors, a plurality of perforations, fivefor example, may be formed in a row transversely to the direction ofmovement of the web at each location where reference marks are desired.A detector is provided for each hole at the detecting station. Logiccircuitry connected to the detectors would pass a signal if, forexample, three of the five detectors gave a signal indicating aperforation. Such an arrangement would ensure proper detection of thereference mark at each location.

Square patterns of four holes may be provided with four detectors todetect both longitudinal and transverse changes in the web. Codedinformation may be applied to the web in forming the perforations in aspecific pattern, this information being invisible to the naked eye butbeing readily read through sensitive light detectors. Various other useswill be apparent to people skilled in the art.

We claim:

1. A method of forming reference marks on a web and measuringcomprising:

accurately locating a reference mark forming station relative to areference mark sensing station in spaced relationship;

forming a first reference mark in said web at said forming station byelectrical means perforating said web; continuously moving said web athigh speeds through said forming and said sensing stations; sensing saidfirst mark at said sensing station and actuating said forming stationupon sensing of said first mark to perforate said web by said electricalmeans and form a second reference mark accurately spaced from said firstmark; sensing said second mark at said sensing station and actuatingsaid forming station upon sensing of said second mark to perforate saidweb by said electrical means and form a third reference mark accuratelyspaced from said second reference mark by the same distance as thespacing between said first and said second marks;

continuing this procedure to form a plurality of accurately positionedreference marks on the web, thereby to form a web having a series ofaccurately spaced reference marks for measuring; and

counting the number of said marks by electrical means thereby to obtainan indication of the length of said web.

2. A method as defined in claim l wherein said reference marks areformed in said forming station by said electrical means burning throughsaid web.

3. A method as defined in claim 2, wherein said electrical meanscomprises an electrical spark passing through said web.

4. A method as defined in claim 2, wherein said electrical meanscomprises a laser beam passing through said web.

5. A method as defined in claim 1, wherein said counting the number ofsaid marks comprises counting said marks sensed at said sensing stationin relation to time to obtain a frequency of marks passing the sensingstation, and computing with electrical means the velocity of the webfrom said frequency, thereby to obtain an indication of the velocity ofthe web.

6. A method as defined in claim 2, wherein said counting the number ofsaid marks comprises counting said marks sensed at said sensing stationin relation to time to obtain a frequency of marks passing the sensingstation, and computing with electrical means the velocity of the webfrom said frequency, thereby to obtain an indication of the velocity ofthe web.

7. A method as defined in claim 3, wherein said counting the number ofsaid marks comprises counting said marks sensed at said sensing stationin relation to time to obtain a frequency of marks passing the sensingstation, and computing with electrical means the velocity of the webfrom said frequency, thereby to obtain an indication of the velocity ofthe web.

with electrical means the velocity of the web from said frequency, theweb.

thereby to obtain an indication of the velocity of

